That's easy: the printing press.

Without it, we wouldn't have had all the computers, telephones, and lightbulbs other people are mentioning.

Also, fire and languange don't count because they weren't invented -- they were discovered.
dannyboy420 Reviewed by dannyboy420 on . What do you think is the greatest invention ever is? Mine has to be light bulbs by Thomas Edison. Simply because they aid us in every day (and night for the pedants) life. It must of been a bitch to use raw fire every time we needed to see artifically. We take them for granted. Big up Thomas Edison. Rating: 5